A vapor recycle type apparatus for obtaining vapor-liquid equilibrium data at low temperatures and high pressures was constructed. Its description and testing are presented. A method of analysis for light hydrocarbons using the infrared spectrophotometer was developed. Curves for the analysis of methane-ethane-propane mixtures are included. Equilibrium data for methane-ethane-propane mixtures at -100°F and at both 215 psia and 365 psia were obtained. Comparisons between the phase compositions predicted from the Kellogg fugacity data and those obtained in this work and in the experimental Methane-Propane and Methane-Ethane systems are shown.